fixed 'Usage' to be on one line instead of two

a comma was left out of the code that produces the Help usage line.  That caused it to print on two lines instead of just one.  This PR adds the missing comma.

also in the same line, when a command line argument has been given a value AND the user has listed --help, we ought show the item that command line argument as an optional value.  In the context of the line provided, it is not optional, it is required. 

This is the case when a program is a launcher and the non-switch argument is a class that represents the app to run.  Git itself is a fine example:

``` bash
$ git commit --help
``` 
the usage line in help should list the word "commit':

``` bash
    git commit  ...
```

earlier configman didn't get this right and would instead show:

``` bash
git [ command ]
```



I know we already have lots of these but these names really aren't helping. 
And having test_massively_long_method_names_that_are_overly_verbose isn't helping either. 
The solution is to contextualize it by breaking things up into smaller classes E.g. `TestOutputSummary.test_single_optional_argument`.

Really just a nit.